Antisperm Antibodies

Some incidences of initially undefined infertility in couples may have a high correlation with immunological problems caused by anti-sperm antibodies

What are Antisperm Antibodies?

Antibodies are proteins produced by the immune system that bind to foreign invaders in the body such as viruses and bacteria. They are one of the ways in which the body discriminates between self and non-self and we would not normally expect our antibodies to bind to our own cells. However, the testes are normally isolated from the immune system and so the sperms themselves do not normally come into contact with the immune system. Exceptionally, such interaction can occur in cases of testicular injury, biopsy or vasectomy reversal and in a few cases a man may even make antibodies against his own sperm. These are called antisperm antibodies. The effect of high levels of these antibodies is to increase agglutination and therefore restrict or immobilise the spermatozoa, impair their cervical mucus penetration, and thereby prevent their progression to the fallopian tube where the egg is waiting to be fertilised.

The antibodies can also have immunoglobulin Ig isotope or antigenic specificity effects but a lack of tests currently available make it difficult to quantify the extent to which these occur.

How Are Anti-Sperm Antibodies Detected?

The mixed antiglobulin reaction (MAR) test is included in some routine semen analyses and this is able to detect antisperm antibodies. Results are usually expressed as the percentage of sperm bound by antibody, and two subclasses of antibody (IgG and IgA) are commonly recorded. Anything less than 10% is considered negative and due to non-specific binding, but there are no concrete reference values for a positive result. The WHO currently regard 50% or greater as a level likely to affect fertility, but this value is pending until further evidence is available. Fertility problems involving antisperm antibodies can usually be successfully overcome using IVF or ICSI.